Expansion drill bit



July 5, 1932. A. E. CARLSON EXPANSION DRILL BIT 4 sheets-Sheet 1 FiledAug. 10 1927 III....

y 1932- A. E. CARLSON ,082

' EXPANSION DRILL BIT Filed Aug. 10. 1927 4 Sheets-Sheet 2 J6 5 34 gz 2541 d6 65 Y Z V July 5, 1932. A. E. cARLsoN 1,366,032

EXPANSION DRILL 1311' Filed Aug. 10. 1927 4 Sheets-Sheet 3 fM/s vrax"WY'TO/PA/EX July 5, '1932. I E, CARLSON 1,866,082

- EXPANSION DRILL BIT Filed Aug. 10 1927 4 Sheets-Sheet 4 7417] GPA/.53.

Patented July 5, 1932 l ANTHQNY\ .E. .GARLSQ1\I, on Losnn-Grmns;GALIEORNIAf ExrANsron nnrLLrm 1 Application filed August 10, 1927'.Serial No. 211,972. r

My invention relatesto'the deep well-drilling: art: andmore particularlyto bits: used as it] drills the hole-for it, the drill being withrotary.drilling; equipment.

Such; rotary equipment includes drill 3 pipe? having drill.bitprovidedon its lower end. The drillpipeextends vertically intothe-earth andis rotatedby a rotary table of thederrick to cause the bitto form a hole. Asa-he bit employed usually has a fixed diam- 1 at.thebottomeiflthe hole. 'Then; afterthe cement hasl h-ardened, a smallerdrill bitiwhich will pass down inside the casing is used" to;

drill through the cement'and deepen the hole.

The deepenedportion of the hole is thenproe' -Vided witha second-casingwhich. extends through the first casing and 31s cemented 1nplacentatherbottom ofthe deepened'portionv H g sltlonsin which they werecloser 'together' ofthe hole. The drilling of the hole is thencontinuedawith astill smaller bit WlllClPWlll pass throughthe secondcasing. The. hole thus; formed receives athirdand still smaller-s casingWhichxis: extended down through the" secondcasing .Thusgthedril'lin g10fthe well continues. until oil is reachedi using-'a'bitof fixed diameter;as above. outlined, each successively deepened portion. of the holeisottsmallen diameter than-the casing through which a bit must be'passedto fornrthat deepened portion Thus, when the "drill bit and stem are.Withdrawn and a casing extended down into this deepened por-Q tion,there is very little spacebetween the from the wellz-bylthis cement. g

It isxan object ofmy invention to provide *anexpansion drillbit whichmay 'beexp'andedg after passing througha casing or after it has beenowered. to the level where itis'toj be operated so-that' theholeiormed-bene aththat casing I may: be: larger than the diameter of Ivention areillustrated. 1

\ several formsjofdrill bits enibodyingniyf in 6 It isanother object toprovide an expansiondrillbltwliich may-be followedby the casing 7adapted to be; contracted and withdrawn through this casing. y x

Expansion bitshave been previously pro-- vided, but these have had'a't'endencyto' collect'mud on the 'cutters s'oas to; form. a-liard ballon the bit so; thatthe bit cannotbe Withloeterawhich is largerthanthe'inside diameter of thecasingto be put-in the hole,-:the hole" isformed to a desired depth and the drill: stem; withdrawn, after which;the. casing is extended into the .hole and cemented in place drawn.upward throughthe casing through which it was extended into the well.Thus, 1t isnecessaryto waste a considerable length of time waiting for.the ball Of l jd; formed on the bit to'dissolve so that the bit may becollapsed'a'nd withdrawn through the casing;

It is' a furtherj object of my invention 'to provide an expansion drill"bit which isv adapted to be operated to break up andremove a ball ofdirt wheneversuch a' ba-ll starts to form on the bit. I j v Expansionbits heretofore produced .re-1 'quired' the collapsing of'the cuttersinto: po

than when ext-ended' into' cutting positi'onyin. order that the bitmight. be" withdrawn 5 through the casing. Many times such contractionis. made impossible dueto the pres ence ofi detrit us'between thecuttersrwhic hi keeps the cutters separated and'preventstheir. movinginto retractedorcollapsed position: It is yet another object of myinvention to provide an expansion drill bit in which a space between thecutters isgreater 1 when these are in retracted or'col lapsedj positionthan when these cuttersare extended po sition.- g I 7 It is of'vi'talimportance to the proper operati'on ofan expansion drill-I'bi-t that"the parts thereof'be fr ee at all tirnes to havefthe proper movementrelative to. eachfothera i It i's-a zfurther object of.my invention toprovide an expansion drill bit in which this freedon'rofthe parts ofthebit isrnaint'ain'ed T by a flushingiaction of'a lubricating-sfluidsupplied thereto. r

Further objects :and' advantages -will be made manifest in thefollowing'description 7 and in the accompanying drawings inwhich 5 Inthe drawings,-' I

Fig. 1 is a side elevational view of one embodiment of my invention withthe cutters thereof in extended position. I

Fig. 2 is a view similar to Fig. 1 in whic the cutters are moved toretracted position.

Fig. 3 is a bottom plan view of Fig. 1. 1

Fig. 4 is a bottom plan viewv of F ig. 2.

Fig. 5 is a vertical sectional View taken on the line 55 of Fig. 3. I 3

Fig. 6 is a horizontal sectional view taken on the line 66 of Fig. 5.

Fig. 7 is a vertical sectional view taken on the line 77 of Fig. 3.

Fig. 8 is a horizontal sectional view taken on the line 88 of 7.

Fig. 9 is a vertical sectional view similar to Fig. 5, illustratingcutter parts'of the drill bit shown in Fig. 5, shifted downward into,zrsecond form of the bit of mylinvention.

Figs. 14 and "15 areihorizontal.sectional views taken on thecorrespondingly numbered lines of Fig. 13. v, V r I 16 is a bottom planview of Fig. 13

partially in section for illustrating the niounting of the cutters upon.theirsupports;

- Fig. 17 is a side elevational view of the drillbit, shownin Fig. 13,taken front the same view-point and showing the cutters, thereofdisposedin retracted position.

I Referring'specifically to the drawings and particularly to Figs. 1 to8, and Hand 12, the numeral 20 indicates one embodiment of the drill bitofgrny invention. This bit includes a body 21 which'has a slight upwardtaper and which is provided with a threaded 1 pin 22 at its-upper endfor securing it to the 7 lower. end of a drill stem. Extending upwardinto the body 21 are bores '23 which are identical in shape andsymmetrically formed onopposite sides of the axis of the body 21.

. The upper end of each ofthe bores 23 is con- 'necte d by a rotary mudpassage 24 which leads to the top of the pin 22 so as to connect 5 zwiththesupply passage of the drill stemv to which the pin is attached.Formed in the body 21- so that each connects with the upperportion ofone of the bores 23 are two threadeddetent' pinholes 25. The upperportion" of the bores 23 are substantially cylindrical, while'the lowerportion is enlarged toward one side thereof. to form a. semiannularfrusto-conical cavity 271 I Each cavity-'27 has radial abutment'faces 28and 29. V

' Extending upward into each ofthe bores 23 is one of a pair ofidentical cutter supports 36. Each of the supports 36, as clearly shownin Fig. 12, has a cylindrical shank 37 which extends into'the upperportion of the bore 23, the shank 37 being turned down at its upper endto provide a pin 38 and a bearing seat 39. Formed in the shank 37 aslight distance below the bearingseat 39 is an annular detent channel40. Formed integrally with the lower portion of the shank 37 is a.semi-annularLfrusto-conical shoulder from which a cutter supporting arm46 extends downward. Formed in the lower end of the leg 46, with itsaxis disposed in crossing relation with, and to one side of, the axis ofthe shank 37, is 'acutter pin bore 50. Adapted to be mounted upon thearm 46 is a cutter 51 which, in the present instance, is-shown as adiscv cutter. The cutter 51 has a central bearing hole 52 and bearingbushings 53 countersunk into opposite faces of; the cutter 51 andsurrounding the hole 52. Passing. through the hole 52 and vthe bushing.53 and extending in the bore by "a key pin 56 which is driven into asuitable: holebored through thearm 46 and the cutter pin55. .The cutter..pins are on horizontal axes A-A which are offset a distance B fromthe-axes C'C of the sup-- ports36;

Extending longitudinally through each cutter support 36 'is a mainlubricating fluid passage 60, the upper end of whichis disposed opposltethe lower end of one of the fluld passages 24-forrned inthe bit body 21and the lower end of which opens from the bottomof the cylindricalshank37 so that the axis thereof intersectsthe upper. edge of the cutter 51carried by thatsupport 36. Lateral fluid passages 62are formed in eachshank 37 and lead from thecentr'al passage therein to the peripheralsurface'of the shank.

Other lateral openings 63 are formed in each shank 37 which lead fromthe central fluid passage 60 and open on oppositesides of the shoulder45.

In assembling the bit 20, an anti-friction thrust bearing 65 is placedaround the pin 38 on each cutter support 36 so that when the supports'36carrying the cutters '51 are extended upward into thebores 23, thethrust bearings 65 abut against the upper ends of the bores 23 so as topermitfree rotation of the supports 36 in the bores 23 within thelnnitsdescribed hereinafter. The supports 36 are retained againstremoval'from the bores 23 by threaded detent pins 68 which are securedinto the threaded holes 25 and project into the detent channels 40.

When the supports 36 are thus -.assembled on the body 21, the shoulders45 are disposed in the cavities 27. As clearly shown-in Fig.

6, the shoulders 45 are formed with their it was extended;

outer frusto-conical surfaces co-aXial with the axis of the shank'37so-that each shoulder 45 is free to rotate in itsrespective cavity 2'?-as its shank 37 rotatesin a bore 28. This rotation of the shank 37 islimited, however to the angular movement between the posi'-' tion' inwhich the shoulder 45' abuts against the abuting face 28 and theposition inwhich that shoulder abuts against the face 29. As clearlyshown in Figs. 3 and 4, the cutters 51 are disposed in extended orcutting position when the shoulders 45 abut against the faces 29, butare disposed in retracted or collapsed position when the shoulders 45abut against the faces 28. I!

'Theoperation of the bit 20-is as follows: The bit is secured upon thelower endofthe drill stem and advanced downward through a string of Wellcasin which is slightly-larger than the maximum diameter of the body 21and while the cutters 51 are in retracted position, as shown in Fig-45..As the bit passes out of the lower end ofthe'casing and approaches thesolid earth at the bottom of the hole, the drill stem is rotatedin arighthand direction which causes the cutters-51 to engage. the earth androtate the supports 36 ninety degrees, so as to bring the shoulders.

tated, will form. a hole considerably larger than the diameter of thebody 21 and also larger than that ofthe casing through which Referringparticularly to Figs. 3 and 4, it will be seen that'the'axes C@ areeccentric of the body 21," and fur ther that the axes A. l A areeccentricof the body 21 and also'of axes C-C. Thus thesup ports 86 areof the-trailing orcastor type and when they are rotated on their axesC'C, the axes A-A are rotated-around the axes C-G; therefore when thesupports IOiSQtQfIOIH the positionsshown in Fig. 4 intothe positionsshown in Fig. 3, the cutters 51 will be swung bodily outward withrespect to the body 21, and will= occupy cutting position as shown.While the bit 20 is being lowered to operating position and also whileit is being operated, the circulation of lubricating fluid, which ingeneral practice is rotary mud, is maintained at alltimes. Thispassesdown through the drill stem, the drill bit passages 24 and 60, and afterlubricating the parts of the bit 20,. passes upward "through the easingcarrying with it the detritus which has been formed by the boring actionof the drill.

Each shank 37 hasatairly loose fit in its respective bore 23 so thatrotarymud will i'iow through the lateral passages 62 and downwardbetween the supports 36 andv the bores 23. This keeps this spacefreefrcm dirt-or other material which might otherwise be forcedthereinto-so as to prevent easy r0- tation of the cutter supports 36when it is desired to swing these to extend or-retract the cutters Asshown.particularly in Figs. 8 and 6, a portionoteach oi the cavities27is open when the shoulders 45' are in either of theirentreniepositionsin these cavi- 27 so astomaintain this entirely clearand thus permit the shoulder 15" to be rotated at any time in thiscavity for thepurposeor manipulating the cutters of the bit. 1' l i Asclearly shown in Figs; 5 and .9, the width of the annular deten-tchannel 40'ofeach cut ter support 36 isgreater' than the diameter of theinner portion of 'thedetent pin 68 which projects into this channel, andthe detent pin, 68 is. so disposed that when the'weight of thebit isplaced upon the cutters thereof, the cutter supports 36 are movedupwardiso that there is a slightspace between the upper :face of thechannels 40 and the detent pin 68. Thus, when the weight of the bit 20is raised from the cutters 51,v the supports 36 drop downward asuiiicient distance so that theiipper face of the channels iOengagesgthe' detent pin. as shown in Fig. 9. This leaves a slight spacebetween each of the shoulders. 45 and the surface of the cavities'27 sothat the'lubricating flui d discharged from the lateral passages 62washes downward-between the O11tQr'1 2CQS'Of. l18 shoulders45 a-nd adiacentportions of the surfaces of the cavities 27, This .flushes outany, foreign matter ugnichinayihave become lodged inthe space Referringspecifically to Figs. 13 50-17 inclusive,.a secondform of thebit ofinvin vention is indicated by the-numeral 80. i The bit has a body 81 whichis substantially cylindrical in shape and is providedwith in threadedpin 82 which extends upward there'- from "and which is adapted toconnect with the lower end of a drill stem upon which the bit80 isadapted to be supported and operated. Extending downward from the upper.end of the pin" 82 into-the'body 81 areniain body 'fluid passages 84:,the lower end of each of which connects to the upper end of one of a par of bores 85 which areidentical and which its are disposedsymmetrically. on opposite sides of the axisof the body The bores 85 areformed 'upwardsfrom the lower end of the body'81; and have openings 86at their lower ends which comunicate laterally with the exteriorof thebody 81. Formed at opposite ends ofeach of the openings 86 are abutmentfaces 87 and 88. Formed centrally'in the y body 8'l-is adetentpin bore90. Connecting the inner end of the bore 90 with the opposite side.ofthe body 81 is a detent' pin-locking are identical.

' cludes a substantially cylindrical shank 96 which has a .pin 97 ofreduced diameter formed at its upper end to'provide a bearing shoulder98 at the'base thereoffDisposed about the pin 97 to rest against theshoulder V 98 is an anti-friction thrust bearing 100.

E.E.which are offset distances G from the ters of my bit are disposedoutwardrfrom the axes of their respective cutter supports in Formed inthe outer surface of the shank 96 a slight distance below the shoulder98 is an annular detentfchannel 101. Formed integrally with the lowerportion of the shank 96 is a shoulder 103. Also formed integrally withthe shank 96 and extending downward therefrom are cutter supporting arms105 and 106, the lower ends of which are spaced apart and provided withaligned cutter pin holes 107and 108in which a cutter pin 109-is receivedand upon which a cutter 110, which in this instance is shown as a disccutter, is rotatably mounted between the legs 105 and 106. The cutterpins '109 are arranged on axes axesFr F of'the supports 95.

Extending longitudinally through each support 95 is a centrallubricating fluid passage 115, the upper end of which is disposedopposite the lower end of the body fluid passage 84 and the lower end ofwhich opens directly'overthe' cutting edge ofthe cutter 1 110 which ismounted uponthat support 95.

Connecting each passage 115 with the ex terior of the shank 96 arelateral passages 120. The central'passage 115-is also connected bylaterals 122 to channels 123 which are formed in the peripheralsurfaceofthe shank 96 so as to be symmetrically disposed in opposite directionsfrom the axis of the shoulder' 103 whichpasses through the axis of theshank96. H

I In assembling the bit 80, the shanks 96 are extended upward into thebores 85 so that the thrust bearinglOO bears against the upper endof thebore 85. The shanks are then rein place by a machine screw 131whichextends through the bore 91 formed for that 'urpose. As clearlshown in Fi 14 o osite portions'of the pin'130 projectinto the detentchannels ,101 of the cutter support shanks 96 so as to prevent thelatter being withdrawn from their respective bores 85.

The shanks 96 have a sufliciently'loose fit within the bores 85 so thatrotary. mud supplied to the bit 80 will flow from the body passage 84and the central cutter support passages 115 through the lateral passages120 and downward through the space between the support shanks '96 andthe inner surface ofthe bores 85. i .Thebit 80 operates in identicallythe same manner as'the bit 20.- A particularly novel featurerof a bit 80is the provision of the cavities 86 so that these open outward andsothat there is almost no chance whatever for these to be filled withdetritus sons to prevent the operation of the bit. The shanks 96 may berotated between the positions in which the shoulders 103 contact theabutment faces 87 and the positions in which the shoulders contact theabutment faces 88. In order to wash out any detritus which might bedisposed in the open portions of the cavities 86, a constant stream offluid flows outward through the lateral passages 122 and thesemi-annular channels 123' while the shoulders 103 are moving towardsone of the abutment faces 87 or 88.

. Another important feature of the bit 80 is theprovision of the arms105 and'106 upon each of the cutterrsupports'95 as amounting for thecutters 110. -The cutters are thus mounted in an extremely rigid mannerso that there is no possibilitythat they could be broken from the bit bystrains incident to the ordinary use thereof.

Owing to the fact that the axes of the cutplanes parallel to the cuttingedges of the cutters, the cutter are practically selfclosing when thebit is drawn upward into the I ble for any detritus to become lodgedbetween the cutters so as to prevent their being retracted. Thegreatest'single drawback of the expansion-bits previously devised isthus entirely overcome, as the possibility of the bitbecoming stuckin'expanded position is eliminated.

I claim as my invention:

1. In an expansion drill bit, the combination of: abit body; cuttersupportspivotally mounted longitudinally therein; cutters rotatablymounted upon said supports, said supports being swingable about theirlongitudinal axes tomove said cutters between retracted and extendedpositions, there being circulation passages in said supports throughwhich lubricating fluid issupplied to said cutters.

2. In an expansion drill bit, the combination of: a bit body havingvertical journal recesses formed upwardly therein; cuter supportsvertically journalled in said recesses to swing transversely about theirvertical axes; cutters rotatably mounted on said supports; means forretaining saidsupports in said recesses; and stop means provided upon Vauxiliary ducts are formed insaid supports said body andsaid supports,limiting rotation of said supports on said body between p si tionsinwhich saidcutters are retracted and position in which said cutters areextended' saidil stop means being so positioned relative to said cuttersthat the planes of the inner facescf'said cutters will move apart assaid cutter supports move-into retractedpos1t1ons.

3, In an expansion dr ll blt, the combmation of: a bit body havingrecesses formed upwardly therein; cutter supports extending intosaidrecesses and" rotatable therein; cutters provlded upon said supports;means' for retaining said supports in said recesses; and stop-meansprovided upon'said body and said supports limiting rotation of saidsupports on said body between'positions inwhich said cutters areretracted and positions in which said cutters are extended, there beingcirculation passages formed in said body and said supports through whichlubricating fluid is supplied to said cutters.

4. A combination asin claim 3 1n which which said cutters'are retractedand positions in which said cutters are extended, said supports'having adegree of longitudinal movement in said recesses when said bit islifted, said movementsettl'ng up a passage between said body andsaidsupports, there being lubricating fluid supply means in said bodyfrom" which said fluid flushes through said passage until said bit isset down. i

6. In an expansiondrill bit, the

distance apart than the inner faces of said cuttersupports when saidcutter supports are swung from retracted into expanded position;

7. In an expansion drill bit, the coriibina-v tion of a body; cuttersupports pivoted to saidbody on substantially vertical" axes, saidvcutter supportsbeing all-times swingablebetween retracted and expandedpositions;

cutters carried by said cutter supports, said cutters being positionedso that imaginary lines drawn throughtheir centersat right angles to theplanes of their cutting edges do not intersect the axis of said cuttersupports;

combina-- tion ofza body; a pair of cutter supports atall timesswing'ab'l'e on said body on a vertical 1 axis; said cutter supportsbeing swingable substantiallyninety degrees; and cutters carried on saidcutter supports in" such positions that the inner faces'of said'cuttersare a greater;

and stops for limiting the swing ofsaidcutter I 7 supports; said stopsbeing so positioned that thein'ner portions of said cutters moveapart assaid supports swing from expanded to retracted position. V V

8}]?11 an expansiondrill b t, the combination of; a body; cuttersupports pivoted to said body on substantially vertical axes, saidcutter 'supports beingiatall times swingabl'e; V i

between retracted and expanded positions; rotary cutters carried by saidcutter supports, said cutters being offset fromthe axes of said cuttersupports; and" stops for limitingthe swing of said cutter supports, saidstops being' so positioned that the inner portions of said cutters-willmove apa'rt'as said supports swing fromexpan'ded to retracted position;

a 9 In an'expansi'on drill bit, thecombination of: abody; cuttersupportspivoted to said body on substantially vertical axes, said cuttersupports being at all times swingabl'e:

between-retracted=and expanded positions; i

cutters carried by; said cutter supports, said cuttersbeing oflse't'fromthe axes of said cutter supports; andstops'tor limiting theswing of said cutter'supports, said stops being;

so positioned that theinnerportionsof said cutters will moveapart'assai'd supports swing from expanded to retracted position.

p '10. In an expansion drill bit, the combination of": "a body; cuttersupports pivoted to said body on substantially vertical axes, saidcutter supportsbeing 'swingable between re-- tracted and expandedpositions; and cutters journalled on said cutter supports, said outtersbeing rotat'able on horizontal axes not intersecting the axes of saidcutter supports and-being so positioned that the projecting peripheriesrot-said; cutters will provide vertically rotatable engagement means forproducing movement of said cutter supports into, retracted positlon whensaid cutters are moved vertically into engagement with an obstruction;

1'1. In'an expansion drill bit, the combina-' tion ofz a bit bodyhavingrecesses formed upwardly therein cutter supports vertically IiOurnalled: in said recesses and at all times rotatable thereincuttersprovided upon said supports means for retaining said supports insaid recesses; {stop meansprovi'ded upon said body and, saId supports,llmlting "rota-i tionof said supports on said ,body between positions inwhich said cutters are retracted, and positions 1n which Said; cuttersare ex-- tended; and means rorisupplying a washing fluid to said stopmeans.

12., In an expansion drill bit,'the combina-- tionoft abody; cuttersupports pivoted tosaid body on substantiallyvertical axes, said cuttersupports beingiat all'tilmes swingable between retracted and; expandedpositions cutterscarried 'saidcutter supports ;;abut j ment faceson-said body and shoulders on said cutter supports, the :retracted' and"ex- 7 I 13.'I n an expansion to said body on substantially verticalaxes,- said cutter supports being swingable between. retractedand'ex'panded positions; and disc panded positions of said cuttersupports being thereby determined, there being passages ex-.

tending directly to the spaces between said abutment faces and shouldersfor directing flushing fluid thereto.

drill bit, the combination of: a body; cutter supports pivoted cuttersrotatable on said cutter supports, said not intersecting the supports.

cutters being rotatable on horizontal axes axes of said cutter 14. In anexpansion drill bit, the combination of: a bit body having verticaljournal bores formed upwardly therein; cutter supports having verticalpivot shanks extending into said bores and adapted for pivotal movementtherein; disc cutters rotatableon saidv supports; means for retainingsaid supports in said bores; stop means provided upon said body and saidsupports, limiting rotation of said supports on said body betweenpositions j in which said cutters are retracted and positions in whichsaid cutters are extended; and means for supplying a washing fluiddirectly to said stop means. c

15. In an expansion drill bit, the combination of: a body; cuttersupports pivoted to said body on substantially vertical axes, saidcutter supports being swingable between re-.

tracted andexpanded positions; disc cutters carried by said cuttersupports; abutment faces on said body; and shoulders on said cuttersupports-the retracted and expanded positions of said cutter-supportsbeing thereby determined, there being passages-extending directlytothespaces between said abutj ment faces and shoulders for directingflushingfluid thereto. V

16. In an expansion drill bit, the combination of :--a body; cuttersupports pivoted to said body on substantially vertical axes, said 7 icuttersupports being'swingable between retracted andexpanded positions;rotary disc cutters operably mounted on said cutter supports, saidcutters beingoffsetfrom the axes of said cutter supports; and stopslimiting l the swinging movement of saidcutter supports, said cuttersand said stops being so positioned relative tov said cutter supports 4.jthat the inner faces of said cutters will move apart as saidcutter'supports move from expanded to retracted position.

-17.'In an expansion drill bit, the combination of: a. body;'cuttersupports of the castor type having cylindrical shanks piv- .oted to saidbody on substantially vertical axes and provided with depending transversely offset legs swingable, between reposing said cutters wider apartin retracted position than in expanded position.

'19. In anexpansion drill bit, the combination of: a body, cuttersupports of the castor type having cylindrical shanks pivoted to saidbody on substantially vertical axes, and provided with dependingtransversely offset legs swingable between retracted and expandedpositions; and cutters carried by the free ends of the legs ofsaidsupports, said cutters being disposed wider apart in the re-.

tracted position of said supports than in the expanded position of saidsupports.

i 20. In an expansion drill bit, the combination of a body, cuttersupports of the castor type having cylindrical shanks pivoted to saidbody on substantially vertical axes and provided with dependingtransversely offset legs swingable between retracted and expandedpositions; and rotary disc cutters carried by the free ends of the legsof said supports,

said cutters being disposed wider apart in the retracted position ofsaid supports than in the expanded position of said supports.

21. In an expansion drill bit, the combination of: a body; cuttersupports of the eastor type having cylindrical shanks pivoted to saidbody on substantially vertical axes and provided withdependingtransversely offset legs swingable between retracted and expandedpositions; cutters carried by the'free ends of'the legs of said cuttersupports; and

means for disposing the confronting faces of said cutters wider apart inretracted position than in expanded position. r

22. In an expansion drill bit, the combination of: a body; a pluralityof cutters having innerportions outlining a space; and

cutter supports for holding said cutters on said body, said cuttersupports rotating relative to said body through arcs and, carrying theinner faces of said cutters into greater spaced relationship and at thesame time carrying said cutters into retracted positions relative tosaid body. 7

In testimony whereof, I have hereunto set my hand at Los Angeles,California, this 5th day of August, 1927. r

, ANTHONY E. CARLSON.

tracted and expandedpositions; cutters car- 7 ried by the free ends ofthe legs of said cutter supports; and means for disposing said bit, thewas.

